/*
 * Created on 23 Jun 2006
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package com.aelitis.azureus.core.networkmanager.impl.udp;

import java.io.IOException;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import org.gudy.azureus2.core3.config.COConfigurationManager;
import org.gudy.azureus2.core3.util.AESemaphore;
import org.gudy.azureus2.core3.util.AEThread2;
import org.gudy.azureus2.core3.util.Debug;
import org.gudy.azureus2.core3.util.SystemTime;

import com.aelitis.azureus.core.networkmanager.impl.TransportHelper;

public class UDPSelector {
    private static final int POLL_FREQUENCY = COConfigurationManager.getIntParameter("network.udp.poll.time", 100);

    private List ready_set = new LinkedList();
    private AESemaphore ready_sem = new AESemaphore("UDPSelector");

    private volatile boolean destroyed;

    protected UDPSelector(final UDPConnectionManager manager) {
        new AEThread2("UDPSelector", true) {
            public void run() {
                boolean quit = false;
                long last_poll = 0;

                while (!quit) {

                    if (destroyed) {

                        // one last dispatch cycle

                        quit = true;
                    }

                    long now = SystemTime.getCurrentTime();

                    if (now < last_poll || now - last_poll >= POLL_FREQUENCY) {

                        manager.poll();

                        last_poll = now;
                    }

                    if (ready_sem.reserve(POLL_FREQUENCY / 2)) {

                        Object[] entry;

                        synchronized (ready_set) {

                            if (ready_set.size() == 0) {

                                continue;
                            }

                            entry = (Object[]) ready_set.remove(0);
                        }

                        TransportHelper transport = (TransportHelper) entry[0];

                        TransportHelper.selectListener listener = (TransportHelper.selectListener) entry[1];

                        if (listener == null) {

                            Debug.out("Null listener");

                        } else {

                            Object attachment = entry[2];

                            try {
                                if (entry.length == 3) {

                                    listener.selectSuccess(transport, attachment);

                                } else {

                                    listener.selectFailure(transport, attachment, (Throwable) entry[3]);

                                }
                            } catch (Throwable e) {

                                Debug.printStackTrace(e);
                            }
                        }
                    }
                }
            }
        }.start();
    }

    protected void destroy() {
        synchronized (ready_set) {

            destroyed = true;
        }
    }

    protected void ready(TransportHelper transport, TransportHelper.selectListener listener, Object attachment)

    throws IOException {
        boolean removed = false;

        synchronized (ready_set) {

            if (destroyed) {

                throw (new IOException("Selector has been destroyed"));
            }

            Iterator it = ready_set.iterator();

            while (it.hasNext()) {

                Object[] entry = (Object[]) it.next();

                if (entry[1] == listener) {

                    it.remove();

                    removed = true;

                    break;
                }
            }

            ready_set.add(new Object[] { transport, listener, attachment });
        }

        if (!removed) {

            ready_sem.release();
        }
    }

    protected void ready(TransportHelper transport, TransportHelper.selectListener listener, Object attachment, Throwable error)

    throws IOException {
        boolean removed = false;

        synchronized (ready_set) {

            if (destroyed) {

                throw (new IOException("Selector has been destroyed"));
            }

            Iterator it = ready_set.iterator();

            while (it.hasNext()) {

                Object[] entry = (Object[]) it.next();

                if (entry[1] == listener) {

                    it.remove();

                    removed = true;

                    break;
                }
            }

            ready_set.add(new Object[] { transport, listener, attachment, error });
        }

        if (!removed) {

            ready_sem.release();
        }
    }

    protected void cancel(TransportHelper transport, TransportHelper.selectListener listener) {
        synchronized (ready_set) {

            Iterator it = ready_set.iterator();

            while (it.hasNext()) {

                Object[] entry = (Object[]) it.next();

                if (entry[0] == transport && entry[1] == listener) {

                    it.remove();

                    break;
                }
            }
        }
    }
}
